Analysis of variable tandem stator load split on the flow characteristics of an adaptive cycle engine fan

To meet the demanding performance requirements of next-generation aero engines especially high maneuverability and extended endurance, adaptive cycle engines (ACE) with three-stream bypass have attracted significant research interest. These engines offer superior operational flexibility through variable geometry and multi-mode adjustment. A key component, the front and rear fan system, must provide an enhanced flow adjustment range for the rear fan and improved throughflow capacity at high Mach numbers. This study investigates a variable tandem stator configuration as a means to address these challenges. Using numerical simulations, we analyze the effect of tandem stator load split (LS) on fan performance. Results indicate that reducing the LS improves both mass flow rate and efficiency: it lowers flow deviation angles and positive pre-swirl at the rear fan inlet, thereby increasing mass flow rate in both front and rear fans and alleviating front surge and rear blockage. While reverse stator adjustment further increases mass flow rate, it also reduces efficiency due to heightened negative pre-swirl and increased reaction degree. During forward adjustment, fans with different LS values exhibit identical stall point mass flow rates, limiting the forward adjustment range for larger LS values. At a lower LS (0.2), the total and internal bypass mass flow rate adjustment ranges exceed 15% and 22%, respectively, significantly greater than those at higher LS (0.6). Moreover, a smaller LS consistently delivers better efficiency across all adjustment angles. Based on these findings, a multi-condition optimization framework is proposed to identify optimal operational parameters under various flight scenarios. This work provides valuable insights into wide-range flow control and variable-condition performance optimization for ACE compression systems.